| People's life is precious .it's very important thing to search find and help people who surfer calamities such as earthquake and terror attack .so we have to development effective life assessment detector and position system to find the suffering people at the first time.We call a signal Ultra-wide-band signal (UWB) when its ratio of bandwidth to center-frequency exceed 25% .UWB signal is characterized by wide band, high resolution .UWB signal's echo could bring abundant message of the objects.The time domain differential method (FDTD) is one powerful tool of computational electromagnetics , which have the advantages of fast computation ,little storage memory and well simulation .because it simulation EM propagation directly in time domain ,it is especially convenient for the transient EM pulse propagation simulation.This paper build the three-dimension FDTD algorithm of UWB EM pulse propagation based on the electromagnetic wave principle and FDTD algorithm. We analyze the energy attenuation character of UWB in the air. it's useful to increase the carrier frequency or shorten the ascending time for slowing down the energy attenuation of the axis. We demonstrate the high frequency have stronger eradiating power than low frequency and high frequency play the important pole in the so-call energy 'slow attenuation'. we analyze the energy attenuation character of UWB through a loss media. when the media is low loss media, it's same useful to increase the carrier frequency or shorten the ascending time. but as the media conductivity increase ,energy attenuation fast. we analyze and compare UWB propagation in the air and encountering loss media with the dipole source. it's found the UWB pulse have focalize mode. at last we give an example of the UWB application. |
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